Stabilizers to inhibit the polymerization of substituted cyclotetrasiloxane

ABSTRACT

The present invention is; (a) a process for stabilizing a cyclotetrasiloxane, such as 1,3,5,7-tetramethylcyclotetrasiloxane, against polymerization used in a chemical vapor deposition process for silicon oxides in electronic material fabrication comprising providing an effective amount of a neutral to weakly acidic polymerization inhibitor to such cyclotetrasiloxane; and (b) a composition of a cyclotetrasiloxane, such as 1,3,5,7-tetramethylcyclotetrasiloxane, stabilized against polymerization used in a chemical vapor deposition process as a precursor for silicon oxides in electronic material fabrication, comprising; such cyclotetrasiloxane and a neutral to weakly acidic polymerization inhibitor. A free radical scavenger can also be included in the process and composition.

BACKGROUND OF THE INVENTION

[0001] Silicon dioxide films have been used for some time in thefabrication of integrated circuits (IC) for semiconductor devicemanufacturing. There are many examples of the preparation of such thinfilms of SiO₂ in the open and patent literature. See, for example, thepublications of the Schumacher Group, Air Products and Chemicals, Inc.,e.g. User's Guide For: Glass Deposition with TEOS¹, and Extrema® TEOS(Tetraethyl Orthosilicate) Product Data Sheet². See also, Modeling ofLow-Pressure Deposition of SiO₂ by Decomposition of TEOS³, and TheDeposition of Silicon Dioxide Films at Reduced Pressure⁴. There arenumerous journal articles that review various CVD techniques for thedeposition of SiO₂ and the properties of thin films deposited using suchtechniques⁵⁻⁹.

[0002] Early SiO₂ films were deposited by CVD oxidation of silane(SiH₄). New source materials were needed in order to maintain good stepcoverage as sub-micron patterned electronic devices were developed.Films deposited from tetraethylorthosilcate (TEOS) show superior stepcoverage properties compared to SiH₄ ⁷. TEOS is considered an industrystandard source for the CVD preparation of SiO₂. TEOS is a volatileliquid, providing for efficient vapor delivery and general ease ofhandling. It is nonpyrophoric, and therefore, provides a significantsafety advantage over silane. It produces dielectric films withexcellent electrical and mechanical properties suitable for many devicemanufacturing applications.

[0003] The chemical 1,3,5,7-Tetramethylcyclotetrasiloxane (such asTOMCATS® siloxane available from Schumacher of Carlsbad, Calif.) isunder development as a new source material for the CVD preparation ofSiO₂ glass¹⁰⁻¹¹. TOMCATS type siloxane is a high purity volatile liquidprecursor chemical that is specifically designed to satisfy the criticaldemands of the semiconductor device manufacturing industry. Like TEOS,TOMCATS type siloxane can be used for the chemical vapor deposition ofglasses and doped glasses for various dielectric film applications suchas trench fill, interlevel dielectric, gate and thick oxide². Itprovides similar safety advantages because of its non-pyrophoric andnoncorrosive nature. The normal boiling points of TOMCATS type siloxaneand TEOS are 135° C. and 168° C., respectively. The higher volatility ofTOMCATS type siloxane allows it to be delivered at lower temperature orwith higher efficiency at comparable temperature. Its deposition rate is10 times that of TEOS at 6000° C., with a deposition efficiency 3 timesthat of TEOS². It is superior to silane and similar to TEOS in theconformality and step coverage of the resulting films¹¹⁻¹².

[0004] In general, SiO₂ films deposited from TOMCATS type siloxaneexhibit excellent mechanical and electrical properties. The films aredense with low carbon content and refractive index values comparable tothermal oxide. TOMCATS type siloxane is effective for low-pressurechemical vapor deposition (LPCVD) and as a liquid injection source forplasma enhanced chemical vapor deposition (PECVD). The later methodutilizes plasmas rather than thermal energy to promote chemicalreactions. TOMCATS type siloxane PECVD is typically run at lowertemperature than LPCVD (400° C. vs. 500-600° C.).

[0005] Despite these advantages, TOMCATS type siloxane has experiencedlimited acceptance as a CVD source for the manufacturing ofsemiconductor devices. One disadvantage of TOMCATS type siloxane is itsinstability with respect to polymerization¹³ when exposed to certainchemicals or process conditions. This results in a lower volatilityliquid or gel that creates CVD process handling issues. TOMCATS typesiloxane polymerization is catalyzed by acid or base. It has beenobserved in the present invention experimentally to be particularlysensitive to exposure to bases (see Examples 9-11 below).

[0006] Prolonged heating of TOMCATS type siloxane (Example 1) has alsobeen shown experimentally in the present invention to promotepolymerization. The degree of polymerization can be very minor,accounting for only several tenths of a percent. Under more severeconditions of prolonged exposure to elevated temperature or to certainacids or bases, substantial polymerization will occur, resulting in ahighly viscous liquid or gel containing over 10% by weight of oligomericor polymeric material.

[0007] Several references in the prior art relate to the stabilizationof siloxane. Hirabayashi et al.¹⁴ teach the use of a triazine or sulfide“control agent” to stabilize a mixture comprising an aliphaticunsaturated group, containing an organopolysiloxane compound, such asTOMCATS type siloxane, and a platinum group catalyst. Those inventorsteach the use of the triazine or sulfide agent to give a mixture that isstable and resistant to premature gelation at room temperature and thusproviding extended storage stability.

[0008] Lutz et al.¹⁵ disclose the use of di- andtrihydrocarbylphosphines which act as curing inhibitors for compositionscomprising: (1) alkenyl radicals; (2) compounds containingsilicon-bonded hydrogen atoms (e.g., TOMCATS type siloxane); and (3) aplatinum group metal catalyst. Lutz et al. claim that the inhibitorfunctions by complexing with the platinum catalyst rendering it inactivefor subsequent curing.

[0009] In a similar patent, Chalk¹⁶ teaches the use of acrylonitriletype compounds that reduce the activity of the platinum catalystdeterring the copolymerization of various mixtures of polysiloxanes.

[0010] Berger et al.¹⁷ propose the use of an ethylenically unsaturatedisocyanurate which functions in a like manner to deactivate the Ptcatalyst rendering a curable organopolysiloxane composition stable topremature gelation.

[0011] Endo et al.¹⁸ teach the stabilization of cyclosiloxanes, such asTOMCATS type siloxane through the use of 1 to 20 weight % ofpolymethylpolysiloxanes, such as 1,1,1,3,5,5,5-heptamethyltrisiloxane.

[0012] The patent references cited all teach the use of various agentsthat in one manner or another inhibit the polymerization orco-polymerization of polysiloxanes for various applications in thesilicon rubber industry. None of them specify or suggest applications aspolymerization inhibitors for CVD sources in the semiconductor devicemanufacturing industry.

BRIEF SUMMARY OF THE INVENTION

[0013] The present invention is a process for stabilizing a substitutedcyclotetrasiloxane against polymerization used in a chemical vapordeposition process for silicon oxides in electronic material fabricationcomprising providing an effective amount of a neutral to weakly acidicpolymerization inhibitor to a substituted cyclotetrasiloxane having thefollowing formula:

[0014] where R¹⁻⁷ are individually selected from the group consisting ofhydrogen, a normal, branched or cyclic C₁₋₁₀ alkyl group, and a C₁₋₄alkoxy group. The process can also include stabilization with a freeradical scavenger.

[0015] The present invention is also a composition of substitutedcyclotetrasiloxane stabilized against polymerization used in a chemicalvapor deposition process as a precursor for silicon oxides in electronicmaterial fabrication, comprising; (a) a substituted cyclotetrasiloxanehaving the following formula:

[0016] where R¹⁻⁷ are individually selected from the group consisting ofhydrogen, a normal, branched or cyclic C₁₋₁₀ alkyl group, and a C₁₋₄alkoxy group, and (b) a neutral to weakly acidic polymerizationinhibitor. The composition can also include a free radical scavenger.

DETAILED DESCRIPTION OF THE INVENTION

[0017] The chemical 1,3,5,7-tetramethylcyclotetrasiloxane (such asTOMCATS® siloxane available from Schumacher of Carlsbad, Calif.) is usedas a precursor for the chemical vapor deposition (CVD) of SiO₂ forsemiconductor device manufacturing. TOMCATS type siloxane is currentlyunder evaluation by semiconductor device manufacturers for use as a CVDprecursors for SiO₂ because of its ability to form high quality filmswith excellent electronic and mechanical properties. TOMCATS typesiloxane is known to polymerize when subjected to extended periods ofheating or upon exposure to certain chemicals. In this invention wedisclose the use of various additives that inhibit the polymerization ofTOMCATS type siloxane. The effective additives are either neutral orweakly acidic with pKa values ranging from 4.88 to 14.15. The lowconcentration of the additive does not significantly impact the overallproduct purity, nor is it anticipated to have a negative impact on thecritical properties of the resulting films produced by CVD.

[0018] Therefore, an object of the present invention is to eliminate orinhibit the polymerization of TOMCATS type siloxane under typical CVDprocess conditions. These TOMCATS type siloxanes include substitutedcyclotetrasiloxanes of the formula:

[0019] where R¹⁻⁷ are individually selected from the group consisting ofhydrogen, a normal, branched or cyclic C₁₋₁₀ alkyl group, and a C₁₋₄alkoxy group.

[0020] This is done through the use of additives that inhibit thepolymerization of TOMCATS type siloxane under conditions that wouldnormally favor polymerization. The present invention demonstrates thatcertain additives are effective at inhibiting polymerization, such as2,4-pentanedione, 1-hexanoic acid, glycerol, acetic anhydride and1,1,1,5,5,5-hexamethyltrisiloxane. Inhibitors contemplated by thepresent invention include: β-diketones, such as RC(O)CH₂C(O)R; aliphaticcarboxylic acids or dicarboxylic acids, such as RCOOH orHOOC—(CH₂)_(n)—COOH in which 1≦n≦8; phenols, such as C₆R(_(6-n))(OH)_(n)in which 1≦n ≦5; polyols, such as CH₂X(CHX)_(n)CH₂X, in which X=H or OHbut at least one X=OH and 1≦n≦8; anhydrides, such asRCH₂—C(O)—O—C(O)—CH₂R; and hydrodosiloxanes, such asR₃Si—(O—SiR₂)_(n)—OSiR₃, in which 0<n <8.R, as used above, isindividually selected from the group consisting of hydrogen, and anormal, branched or cyclic C₁₋₁₀ alkyl group.

[0021] Comparative data are also included (Example 8 and Table 1) whichestablish that 1,1,1,3,5,5,5-heptamethyltrisiloxane is an effectiveadditive that deters polymerization when present at concentrations wellbelow that described in the prior art¹⁸. These additives arecollectively characterized as neutral to weakly acidic. The additivesidentified herein contain only carbon, oxygen, hydrogen and silicon, asin the latter case of the siloxanes, which give rise to volatiledecomposition products such as H₂O and CO/CO₂ in the CVD process.Furthermore, the additives were found to be effective at low enoughconcentrations, such that they do not significantly impact the overallpurity of TOMCATS type siloxane.

[0022] Additional additives constituting free radical scavengers canalso be added to the substituted cyclotetrasiloxanes. TOMCATS typesiloxanes are sensitive to oxygen at elevated temperatures. TOMCATS typesiloxanes react with oxygen forming oligomeric and polymeric species attemperatures equal to or greater than 60° C. This is significant becauseoxygen is commonly used as the oxidizing gas in plasma enhanced chemicalvapor deposition (PECVD) processes for the deposition of SiO₂ films fromTOMCATS type siloxane. These scavengers work by deterring chemicalreactions that proceed by a free-radical reaction pathway. The freeradical scavengers contemplated as O₂-stabilizers are2,6-di-tert-butyl-4-methyl phenol (or BHT for butylhydroxytoluene),2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO),2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, propylester 3,4,5-trihydroxy-benzoic acid,2-(1,1-dimethylethyl)-1,4-benzenediol, diphenylpicrylhydrazyl,4-tert-butylcatechol, N-methylaniline, p-methoxydiphenylamine,diphenylamine, N,N′-diphenyl-p-phenylenediamine, p-hydroxydiphenylamine,phenol, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate,tetrakis (methylene (3,5-di-tert-butyl)-4-hydroxy-hydrocinnamate)methane, phenothiazines, alkylamidonoisoureas, thiodiethylene bis(3,5,-di-tert-butyl-4-hydroxy-hydrocinnamate, 1,2,-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl) hydrazine, tris(2-methyl-4-hydroxy-5-tert-butylphenyl) butane, cyclic neopentanetetraylbis (octadecyl phosphite), 4,4′-thiobis (6-tert-butyl-m-cresol),2,2′-methylenebis (6-tert-butyl-p-cresol), oxalyl bis(benzylidenehydrazide) and naturally occurring antioxidants such as rawseed oils, wheat germ oil, tocopherols and gums.

[0023] To attain the object of the present invention to eliminate orinhibit the polymerization of TOMCATS type siloxane under typical CVDprocess conditions, a standard laboratory test was established with theintent of accelerating the normal polymerization process. Theaccelerated aging test is meant to simulate the normal course of gradualpolymerization that would typically occur over a more protracted periodof time. This test, which consists of exposing a sealed quartz ampouleof TOMCATS type siloxane to elevated temperature for 5 days, is referredto in the present document as the “accelerated aging test”. Theseconditions are understood to be considerably more severe than TOMCATStype siloxane would be subjected to in a typical CVD process. In atypical accelerated aging test, the ampoule is loaded with 3.0-7.0 ml ofTOMCATS type siloxane and possibly an additive to inhibitpolymerization. The TOMCATS type siloxane/additive mixture is cooled ina liquid nitrogen bath. Then, the atmosphere above the TOMCATS typesiloxane is evacuated for 5 minutes. The neck of the quartz ampoule issubsequently sealed using a hydrogen/oxygen torch. The sealed ampoule isplaced in an oven and held at 120° C. for 5 days. The ampoule is removedand allowed to cool to room temperature. Its contents are analyzed bygas chromatograph (GC) to measure the degree of polymerization.

[0024] The degree of polymerization is measured quantitatively by GC.This technique is very sensitive to detecting the onset ofpolymerization as evidenced by the formation of higher molecular weightspecies with longer retention times than the parent TOMCATS typesiloxane peak. TOMCATS type siloxane samples that are determined to beof “high viscosity” by visual inspection are not routinely run on theGC. The oligomeric or polymeric siloxanes tend to irreversiblycontaminate the stationary phase of the GC column due to their lowsolubility and low volatility. Such samples are qualitatively describedin the present invention to have greater than 10 wt. % polymer,consistent with previous observations.

[0025] The polymerization of cyclical polysiloxanes is known to becatalyzed by either acid or base. Laboratory observations suggest thatthe polymerization of TOMCATS type siloxane is particularly sensitive toexposure to bases such as ammonia (NH₃) or ammonium hydroxide (NH₄OH).The result of exposure of TOMCATS type siloxane to base is described inExamples 9-11. In general, additives which are neutral to weakly acidicin low concentration were found to be effective at inhibitingpolymerization. Weakly acidic additives, with pKa values ranging from4.88 to 14.15 substantially minimized the degree of TOMCATS typesiloxane polymerization. This is illustrated in Examples 2-4 and 6.Similarly, acetic anhydride, which is neutral on an acid-base scale, wasalso shown to inhibit polymerization as shown in Example 5. Theadditives were generally found to be effective over the concentrationrange of 100-1000 ppm (0.01-0.10%). This additive concentration is lowenough such that it does not significantly impact the overall purity ofthe chemical relative to the additive-free source material. None of theadditives contain nitrogen that is believed to have a detrimental impacton the quality of the resulting CVD films. The additives described inthis invention form solutions with TOMCATS type siloxane at the testedconcentrations. In addition, these additives are not anticipated to havea detrimental impact on the overall CVD process by virtue of theirconcentration and their chemical and physical characteristics.

EXAMPLE 1

[0026] Blank

[0027] In general a one or two blanks (additive-free TOMCATS typesiloxane) were run for every set of stability experiments described inthis invention. Several different batches of TOMCATS type siloxanesource material were used. For the sake of clarity, all the results fromthe blank experiments were included in this example. The volume of theampoules used for these tests was typically 80-90 ml. The quartzampoules were routinely cleaned by rinsing with distilled water, thenwith reagent grade acetone. The rinsed ampoules were placed into adrying oven at 175° C. for a minimum of 4 hours. The dry ampoules wereremoved from the oven and used while still warm. 3.0-7.0 ml of TOMCATStype siloxane were loaded into each ampoule. Teflon valves were attachedto the open end of the ampoules, and the TOMCATS type siloxane wascooled by immersing the end of the ampoules into a liquid nitrogen bath.The air was removed from the ampoules by subjecting them to vacuum for 5minutes. The ampoules were sealed at the neck using a hydrogen/oxygentorch. The sealed ampoules were placed in a nitrogen-purged oven held ata constant temperature of 120° C. for 5 days. After 5 days the ampouleswere removed from heat and allowed to cool to room temperature. If thesamples were deemed to be highly viscous or solid by visual inspectionthey were not analyzed by GC, but instead they were assigned a degree ofpolymerization of “>10 wt. %.” The value of >10 wt. % was based on GCanalysis of previous samples that had undergone a similar viscosityincrease. Again, GC analysis was not carried out for extensivelypolymerized samples because high levels of polymer tended toirreversibly contaminate the GC column. The blank TOMCATS type siloxanesamples described in this example showed an increase in polymerizationranging from 0.18 wt % to >10 wt. %. The results are summarized in Table1.

EXAMPLE 2

[0028] Spike of 100 ppm of 2,4-pentanedione

[0029] In a typical experiment 0.50 microliters of 2,4-pentanedione wasadded to an ampoule previously cleaned and dried as described inExample 1. To this ampoule 5.0 ml of TOMCATS type siloxane was added,taking care to rinse down any residual 2,4-pentanedione liquid thatremained adhered to the inner wall of the ampoule. The ampoule thusprepared contained TOMCATS type siloxane with 100 ppm by volume of2,4-pentanedione. The ampoule was sealed and heated for 5 days at 120°C. as described in Example 1. There was no detectable change in theviscosity, color or clarity of the TOMCATS type siloxane sample byvisual inspection after the completion of the accelerated aging test ascompared to the pristine sample prior to testing. Similar tests weredone on 3.0 ml to 7.0 ml samples of TOMCATS type siloxane spiked with100 ppm of 2,4-pentanedione additive. In each case there was nodetectable visible changes in the sample after testing. These samplesshowed an increase in polymerization ranging from no increase to 0.35wt. %. The results are summarized in Table 1.

EXAMPLE 3

[0030] Spike of 1000 ppm of 2,4-pentanedione

[0031] In a typical experiment 5.0 microliters of 2,4-pentanedione wasadded to an ampoule previously cleaned and dried as described inExample 1. To this ampoule 5.0 ml of TOMCATS type siloxane was added,taking care to rinse down residual 2,4-pentanedione liquid that remainedadhered to the inner wall of the ampoule. The ampoule thus preparedcontained TOMCATS type siloxane with 1000 ppm by volume of2,4-pentanedione. The ampoule was sealed and heated for 5 days at 120°C. as described in Example 1. There was no detectable change in theviscosity, color or clarity of the TOMCATS type siloxane sample byvisual inspection after the completion of the accelerated aging test ascompared to the pristine sample prior to testing. Similar tests weredone on 3.0 ml to 7.0 ml samples of TOMCATS type siloxane spiked with100 ppm of 2,4-pentanedione additive. In each case there was nodetectable visible changes in the sample after testing. These samplesshowed an increase in polymerization ranging from 0.11 wt. % to 0.30 wt.%. The results are summarized in Table 1.

Example 4

[0032] Spike of 100-1000 ppm of 1-hexanoic Acid

[0033] 0.70 microliters and 3.0 microliters of 1-hexanoic acid wereadded to each of two ampoules previously cleaned and dried as describedin Example 1. 7.0 ml and 3.0 ml of TOMCATS type siloxane were added toeach of these ampoules, respectively, taking care to rinse down residual1-hexanoic acid liquid that remained adhered to the inner wall of theampoules. The ampoules thus prepared contained TOMCATS type siloxanewith 100 ppm (vol.) and 1000 ppm (vol.) of 1-hexanoic acid,respectively. The ampoules were sealed and heated for 5 days at 120° C.as described in Example 1. There were no detectable changes in theviscosity, color or clarity of the TOMCATS type siloxane sample byvisual -inspection after the completion of the accelerated aging test ascompared to the pristine sample prior to testing. The GC data showed anincrease in polymerization of 0.08 wt. % and 2.84 wt. % for the TOMCATStype siloxane samples spiked with 100 ppm and 1000 ppm of additive,respectively. Results are summarized in Table 1.

EXAMPLE 5

[0034] Spike of 100-1000 ppm of Acetic Anhydride

[0035] 0.50 microliters and 5.0 microliters of acetic anhydride wereadded to each of two ampoules previously cleaned and dried as describedin Example 1. 5.0 ml of TOMCATS type siloxane was added to each ampouletaking care to rinse down residual acetic anhydride liquid that remainedadhered to the inner wall of the ampoules. The ampoules thus preparedcontained TOMCATS type siloxane with 100 ppm (vol.) and 1000 ppm (vol.)of acetic anhydride, respectively. The ampoules were sealed and heatedfor 5 days at 120° C. as described in Example 1. There were nodetectable changes in the viscosity, color or clarity of the TOMCATStype siloxane sample by visual inspection after the completion of theaccelerated aging test as compared to the pristine sample prior totesting. These tests were repeated twice more for each additiveconcentration. The GC data showed an increase in polymerization of 0.08wt. % to 0.38 wt. % for the TOMCATS type siloxane samples spiked with100 ppm of additive; and an increase in polymerization of 0.14 wt. % to0.38 wt. % for the TOMCATS type siloxane samples spiked with 1000 ppm ofadditive. The results are summarized in Table 1.

EXAMPLE 6

[0036] Spike of 100 ppm of Glycerol

[0037] 0.61 mg (0.48 microliters) of glycerol was added to an ampoulepreviously cleaned and dried as described in Example 1. 5.0 ml ofTOMCATS type siloxane was added to the ampoule taking care to rinse downresidual glycerol liquid that remained adhered to the inner wall of theampoule. The ampoule thus prepared contained TOMCATS type siloxane with100 ppm (vol.) of glycerol. The ampoule was sealed and heated for 5 daysat 120° C. as described in Example 1. There was no detectable change inthe viscosity, color or clarity of the TOMCATS type siloxane sample byvisual inspection after the completion of the accelerated aging test ascompared to the pristine sample prior to testing. The GC data showed anincrease in polymerization of 0.12 wt. % for the TOMCATS type siloxanesamples spiked with 100 ppm of additive. The results are summarized inTable 1.

EXAMPLE 7

[0038] Spike of 1,1,1,5,5,5-hexamethyltrisiloxane

[0039] 3.0 microliters and 30 microliters of1,1,1,5,5,5-hexamethyltrisiloxane were added to each of two ampoulespreviously cleaned and dried as described in Example 1. 3.0 ml ofTOMCATS type siloxane was added to each ampoule taking care to rinsedown residual 1,1,1,5,5,5-hexamethyltrisiloxane liquid that remainedadhered to the inner wall of the ampoules. The ampoules thus preparedcontained TOMCATS type siloxane with 1000 ppm and 10,000 ppm (vol.) of1,1,1,5,5,5-hexamethyltrisiloxane, respectively. The ampoules weresealed and heated for 5 days at 120° C. as described in Example 1. Therewere no detectable changes in the viscosity, color or clarity of theTOMCATS type siloxane sample by visual inspection after the completionof the accelerated aging test as compared to the pristine sample priorto testing. The GC data showed an increase in polymerization of 0.20 wt.% and 0.66 wt. % for the TOMCATS type siloxane samples spiked with 1000ppm and 10,000 ppm of additive, respectively. The results are summarizedin Table 1.

EXAMPLE 8

[0040] Spike of 1,1,1,3,5,5,5-heptamethyltrisiloxane

[0041] 0.30, 30 and 150 microliters of1,1,1,3,5,5,5-heptamethyltrisiloxane were added to each of threeampoules previously cleaned and dried as described in Example 1. 3.0 mlof TOMCATS type siloxane was added to each ampoule taking care to rinsedown residual 1,1,1,3,5,5,5-heptamethyltrisiloxane liquid that remainedadhered to the inner wall of the ampoules. The ampoules thus preparedcontained TOMCATS type siloxane with 100 ppm (vol.), 10,000 ppm (vol.)and 50,000 ppm (vol.) of 1,1,1,3,5,5,5-heptamethyltrisiloxane,respectively. The ampoules were sealed and heated for 5 days at 120° C.as described in Example 1. There were no detectable changes in theviscosity, color or clarity of the TOMCATS type siloxane sample byvisual inspection after the completion of the accelerated aging test ascompared to the pristine sample prior to testing. The GC data showed anincrease in polymerization of up to 0.33 wt. % for the TOMCATS typesiloxane samples spiked with the aforementioned levels of additive.Results are summarized in Table 1.

[0042] Example 8 is a comparative example in which accelerated agingtests are carried out on a sample of TOMCATS type siloxane spiked withvarious levels of 1,1,1,3,5,5,₇5-heptamethyltrisiloxane ranging from 100ppm to 50,000 ppm (5%) by weight. This example illustrates that theheptamethyltrisiloxane is effective at inhibiting polymerization atconcentrations below the 1 wt. % lower limit claimed by Endo et. al¹⁸.

EXAMPLE 9

[0043] Spike of 15 ppm and 150 ppm of Anhydrous Ammonia

[0044] Two 100 ml Pyrex Schlenk flasks equipped with side arms andstopcocks were connected to a vacuum line. The flasks were thoroughlydried by heating intermittently with a hydrogen/oxygen torch whilepulling a vacuum on the flasks through the side arms. The flasks wereisolated from the vacuum line by closing the stopcock valves on the sidearms. 5.0 ml of TOMCATS type siloxane was introduced into each of theflasks by injection with a syringe through the rubber septum on the topof the flask. The two flasks were back-filled with dry nitrogen gas toambient pressure. 0.10 ml and 1.0 ml of anhydrous ammonia gas wereintroduced into each of the two flasks. The flasks thus preparedcontained TOMCATS type siloxane spiked with 15 ppm and 150 ppm ammoniaby weight, respectively. The flasks were allowed to stand at roomtemperature for 24 hours. One ml aliquots of TOMCATS type siloxane wereremoved from each of the two flasks by syringe 2 hours and 20 hoursafter the beginning of the test. The four samples were analyzed by GC todetermine the extent of polymerization. The sample of TOMCATS typesiloxane spiked with 15 ppm of NH₃ showed increases in polymerization of0.11% and 0.18% after 2 hours and 20 hours, respectively. The sample ofTOMCATS type siloxane spiked with 150 ppm of NH₃ showed increases inpolymerization of 0.10% and 0.17% after 2 hours and 20 hours,respectively. The results are summarized in Table 2.

EXAMPLE 10

[0045] Siloxane/100 ppm of 2,4-pentanedione Spiked with 15 ppm and 150ppm of Anhydrous Ammonia

[0046] Two 100 ml Pyrex Schlenk flasks were dried by heating on thevacuum line as described in Example 9. 0.5 microliters of2,4-pentanedione was added to each of the flasks using a 1.0 microlitersyringe. 5.0 ml of TOMCATS type siloxane was subsequently introducedinto each of the flasks by injection with a syringe through the rubberseptum on the top of the flask. The TOMCATS type siloxane was added insuch a manner to ensure that residual 2,4-pentanedione was thoroughlyrinsed down from the sides of the flask. The two flasks were back-filledwith dry nitrogen gas to ambient pressure. 0.10 ml and 1.0 ml ofanhydrous ammonia gas were introduced into each of the two flasks. Thetwo flasks thus prepared contained 100 ppm of 2,4-pentanedione inTOMCATS type siloxane spiked with 15 ppm and 150 ppm ammonia by weight,respectively. The flasks were allowed to stand at room temperature for24 hours. One ml aliquots were removed from each of the two flasks bysyringe 2 hours and 20 hours after the beginning of the test. The foursamples were analyzed by GC to determine the extent of polymerization.The sample of TOMCATS type siloxane spiked with 15 ppm of NH₃ showed0.08% polymerization after 2 hours and 20 hours, respectively. Thesample of TOMCATS type siloxane spiked with 150 ppm of NH₃ showed 0.07%and 0.09% polymerization after 2 hours and 20 hours, respectively. Theresults are summarized in Table 2.

EXAMPLE 11

[0047] Exposure to 1.0 wt. % Anhydrous Ammonia

[0048] 5.0 ml of TOMCATS type siloxane was added to each of two ampoulespreviously cleaned and dried as described in Example 1. Each of theampoules was equipped with a side arm capped with a rubber septum. TheTOMCATS type siloxane samples in the ampoules were cooled by submersionin a liquid nitrogen bath. The air was removed from the ampoules byexposing to vacuum conditions for 5 minutes. At this time the ampouleswere isolated from the vacuum and 72 ml of anhydrous ammonia gas (atambient pressure) was injected through the rubber septa into each of theampoules. This corresponds to 1.0 wt. % NH₃-99.0 wt. % TOMCATS typesiloxane. The ampoules were sealed under vacuum with a torch asdescribed in Example 1. The liquid nitrogen was removed and the TOMCATStype siloxane/ammonia mixtures were allowed to slowly warm to roomtemperature. The liquid was noticed to be quite viscous within 30minutes after warming to room temperature. The ampoules were heated for5 days at 120° C. as described in Example 1. The ampoules were removedfrom the oven and allowed to cool to room temperature. The TOMCATS typesiloxane liquid had become highly viscous, similar in consistency tomolasses. The samples were determined to be too polymerized to analyzeby GC and were assigned a degree of polymerization of >10 wt. %. TABLE 1TOMCATS type siloxane Accelerated Aging Tests Using Various AdditivesTOMCATS TOMCATS type siloxane type siloxane Increase in Additive andConcentration pKa of purity (wt. %) purity (wt. %) polymerization Ex.Run # by volume additive pre-test post-test (wt. %) Run #1 (a) Blank (noadditive) N.A 99.80 <90% >10 Run #1 (b) Blank (no additive) N.A 99.80<90% >10 Run #1 (c) Blank (no additive) N.A 99.80 99.54 0.26 Run #1 (d)Blank (no additive) N.A 99.80 99.61 0.19 Run #1 (e) Blank (no additive)N.A 99.21 90.52 8.69 Run #1 (f) Blank (no additive) N.A 99.62 99.44 0.18Run #1 (g) Blank (no additive) N.A 99.62 <90% >10 Run #1 (h) Blank (noadditive) N.A 99.54 98.00 1.54 Run #2 (a) 100 ppm 2,4-pentanedione 9.099.80 99.76 0.03 Run #2 (b) 100 ppm 2,4-pentanedione 9.0 99.62 99.550.06 Run #2 (c) 100 ppm 2,4-pentanedione 9.0 99.62 99.26 0.35 Run #2 (d)100 ppm 2,4-pentanedione 9.0 99.62 99.35 0.26 Run #2 (e) 100 ppm2,4-pentanedione 9.0 99.54 99.54 0.00 Run #2 (f) 100 ppm2,4-pentanedione 9.0 99.54 99.53 0.00 Run #3 (a) 1000 ppm2,4-pentanedione 9.0 99.80 99.40 0.30 Run #3 (b) 1000 ppm2,4-pentanedione 9.0 99.62 99.40 0.12 Run #3 (c) 1000 ppm2,4-pentanedione 9.0 99.62 99.41 0.11 Run #4 (a) 100 ppm 1-hexanoic acid4.88 99.80 99.71 0.08 Run #4 (b) 1000 ppm 1-hexanoic acid 4.88 99.8096.86 2.84 Run #5 (a) 100 ppm acetic anhydride N.A 99.62 99.53 0.08 Run#5 (b) 100 ppm acetic anhydride N.A 99.62 99.47 0.14 Run #5 (c) 100 ppmacetic anhydride N.A 99.62 99.23 0.38 Run #5 (d) 1000 ppm aceticanhydride N.A 99.62 99.38 0.14 Run #5 (e) 1000 ppm acetic anhydride N.A99.62 99.30 0.22 Run #5 (f) 1000 ppm acetic anhydride N.A 99.62 99.140.38 Run #6 (a) 100 ppm glycerol 14.15 99.62 99.49 0.12 Run #7 (a) 1000ppm 6MTS* 99.80 99.50 0.20 Run #7 (b) 10,000 ppm 6MTS* 99.80 98.14 0.66Run #8 (a) 100 ppm 7MTS** 99.80 99.46 0.33 Run #8 (b) 10,000 ppm 7MTS**99.80 98.73 0.07 Run #8 (c) 50,000 ppm 7MTS** 99.80 95.46 0

[0049] TABLE 2 The Effect of 2,4-Pentanedione to Limit thePolymerization of TOMCATS type siloxane Containing Low Levels ofAnhydrous Ammonia Gas 2,4- NH₃ pentane- % % concen- dione PolymerizationPolymerization tration conc. by after 2 hours after 20 hours Ex. Run #by weight weight at 25° C. at 25° C. Run #9 (a)  15 ppm none 0.11 0.18Run #9 (b) 150 ppm none 0.10 0.17 Run #10 (a)  15 ppm 100 ppm 0.08 0.08Run #10 (b) 150 ppm 100 ppm 0.07 0.09

[0050] In-house experiments have established that TOMCATS type siloxaneis sensitive to oxygen at elevated temperatures. TOMCATS type siloxanereacts with oxygen forming oligomeric and polymeric species attemperatures equal to or greater than 60° C. This is particularlyimportant since oxygen is commonly used as the oxidizing gas in PECVDprocesses for the deposition of SiO₂ films from TOMCATS type siloxane.Data collected in the 22° C. to 120° C. range are shown in Table 3.

[0051] The preferred additive, 2,4-pentanedione, does not prevent thepolymerization of TOMCATS type siloxane in the presence of oxygen. Toaddress this reactivity TOMCATS type siloxane was spiked with low levelsof chemicals which function as free radical scavengers, i.e.,antioxidants. These scavengers work by deterring chemical reactions thatproceed by a free-radical reaction pathway. The free radical scavengersinvestigated as O₂-stabilizers were 2,6-di-tert-butyl-4-methyl phenol(or BHT for butylhydroxytoluene) and2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). TOMCATS type siloxane wassubstantially more resistant toward O₂ when spiked with either one ofthese free radical scavengers. The addition of 50-500 ppm of BHTcompletely eliminated the reactivity of TOMCATS type siloxane towardoxygen at elevated temperature as shown by the series of tests run at80° C. Another benefit is that BHT is free of atomic nitrogen whichreportedly gives rise to undesirable basic film properties. TEMPO wasalso shown to be an effective O₂-stabilizer. Addition of 50-230 ppm ofTEMPO to TOMCATS type siloxane reduced the degree of O₂-promotedpolymerization by over 80% (Table 3).

[0052] These tests clearly established the benefit of the use of lowlevels of free radical scavengers to greatly reduce or eliminate thesensitivity of TOMCATS type siloxane to oxygen, thereby, reducing thelikelihood of plugging problems occurring by the oxygen promotedpolymerization of TOMCATS type siloxane. The scavengers/antioxidantscontemplated for this utility include: 2,6-di-tert-butyl-4-methylphenol, 2,2,6,6-tetramethyl-1-piperidinyloxy,2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, propylester 3,4,5-trihydroxy-benzoic acid,2-(1,1-dimethylethyl)-1,4-benzenediol, diphenylpicrylhydrazyl,4-tert-butylcatechol, N-methylaniline, p-methoxydiphenylamine,diphenylamine, N,N′-diphenyl-p-phenylenediamine, p-hydroxydiphenylamine,phenol, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate,tetrakis (methylene (3,5-di-tert-butyl)-4-hydroxy-hydrocinnamate)methane, phenothiazines, alkylamidonoisoureas, thiodiethylene bis(3,5,-di-tert-butyl-4-hydroxy-hydrocinnamate, 1,2,-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl) hydrazine, tris(2-methyl-4-hydroxy-5-tert-butylphenyl) butane, cyclic neopentanetetraylbis (octadecyl phosphite), 4,4′-thiobis (6-tert-butyl-m-cresol),2,2′-methylenebis (6-tert-butyl-p-cresol), oxalyl bis(benzylidenehydrazide) and mixtures thereof. Naturally occurringantioxidants can also be used such as raw seed oils, wheat germ oilstocopherols and gums. TABLE 3 TOMCATS type siloxane/Oxygen CompatibilityTests Five day aging tests were conducted at 22° C., 60° C., 80° C., 90°° C. and 120° C. For all of these tests TOMCATS type siloxane containing100 ppm of 2,4-pentanedione was exposed to 0.5 wt. % O₂. Scavenger Free-Concen- Temperature Radical tration % Polymerization* Ex. Run # (° C.)Scavenger (ppm) 1 day 5 days Run # 11 (a) 120 None 0 7.1 7.9 Run # 11(b) 90 None 0 6.8 7.0 Run # 11 (c) 80 None 0 not 5.1 collected Run # 11(d) 60 None 0 1.7 6.8 Run # 11 (e) 22 None 0 0.0 0.0 Run # 12 (a) 80 BHT50 not 0.10 collected Run # 12 (b) 80 BHT 100 not 0.03 collected Run #12 (c) 80 BHT 200 not 0.04 collected Run # 12 (d) 80 BHT 500 not 0.05collected Run # 13 (a) 80 TEMPO 50 not 0.82 collected Run # 13 (b) 80TEMPO 100 not 0.82 collected Run # 13 (c) 80 TEMPO 230 not 0.88collected

EXAMPLE 12

[0053] Reactivity of Oxygen Spike of 100 ppm of 2,4-pentanedione

[0054] 0.50 microliters of 2,4-pentanedione was added to an ampoulepreviously cleaned and dried as described in Example 1. The ampoule wasequipped with a quartz side arm extension capped with a septum. To thisampoule 5.0 ml of TOMCATS type siloxane was added, taking care to rinsedown any residual 2,4-pentanedione liquid that remained adhered to theinner wall of the ampoule. The ampoule thus prepared contained TOMCATStype siloxane with 100 ppm by volume of 2,4-pentanedione. The ampoulewas cooled to liquid nitrogen temperature and evacuated to remove air.The ampoule was isolated from the vacuum and a pre-determined amount ofoxygen was injected through the side arm. Two ampoules prepared in thismanner were sealed and heated for 1 day at 120° C. as described inExample 1. Two additional ampoules prepared in like manner were heatedfor 5 days. These samples showed an average increase in polymerizationof 7.1% and 7.9% after one day and after 5 days, respectively.

[0055] This set of tests was repeated at 90° C., 80° C., 60° C. and 22°C. Data were collected only after 5 days for the 80° C. test.Significant polymerization again occurred at 90° C., 80° C. and 60° C.,but was absent at 22° C. The data are summarized in Table 3.

EXAMPLE 13

[0056] Reactivity of Oxygen Spike of 100 ppm of 2,4-pentanedione and50-500 ppm of BHT

[0057] 0.50 microliters of 2,4-pentanedione was added to an ampoulepreviously cleaned and dried as described in Example 1. The ampoule wasequipped with a quartz side arm extension capped with a septum. 5.0 mlof TOMCATS type siloxane containing 50 ppm of dissolved BHT was added tothe ampoule. The ampoule thus prepared contained TOMCATS type siloxanewith 100 ppm by volume of 2,4-pentanedione and 50 ppm BHT. The ampoulewas cooled to liquid nitrogen temperature and evacuated to remove air.The ampoule was isolated from the vacuum and a pre-determined amount ofoxygen was injected through the side arm. Two ampoules prepared in thismanner were sealed and heated for 5 days at 80° C. as described inExample 1. These duplicate samples showed an increase in polymerizationof 0.05% and 0.15% for an average of 0.10%. The data are summarized inTable 3.

[0058] The above tests were repeated in duplicate using 100 ppm, 200 ppmand 500 ppm of BHT. Less than 0.05% polymerization increase was observedfor each of these three levels of BHT additive.

EXAMPLE 14

[0059] Reactivity of Oxygen Spike of 100 ppm of 2,4-pentanedione and50-230 ppm of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)

[0060] 0.50 microliters of 2,4-pentanedione was added to an ampoulepreviously cleaned and dried as described in Example 1. The ampoule wasequipped with a quartz side arm extension capped with a septum. 5.0 mlof TOMCATS® containing 50 ppm of dissolved TEMPO was added to theampoule. The ampoule thus prepared contained TOMCATS type siloxane with100 ppm by volume of 2,4-pentanedione and 50 ppm TEMPO. The ampoule wascooled to liquid nitrogen temperature and evacuated to remove air. Theampoule was isolated from the vacuum and a pre-determined amount ofoxygen was injected through the side arm. Two ampoules prepared in thismanner were sealed and heated for 5 days at 80° C. as described inExample 1. These samples showed an increase in polymerization of 0.89%and 0.76% for an average of 0.82%. The data are summarized in Table 3.

[0061] The above tests were repeated in duplicate using 100 ppm and 230ppm of TEMPO. TOMCATS type siloxane spiked with these levels of TEMPOunderwent 0.82% and 0.88% increase in polymerization, respectively.

[0062] The present invention has been set forth with regard to severalpreferred embodiments, but the full scope of the present inventionshould be ascertained from the claims which follow.

1. A process for stabilizing a cyclotetrasiloxane against polymerizationused in a chemical vapor deposition process for silicon oxides inelectronic material fabrication, comprising; providing an effectiveamount of a neutral to weakly acidic polymerization inhibitor to saidcyclotetrasiloxane having the following formula:

where R¹⁻⁷ are individually selected from the group consisting ofhydrogen, a normal, branched or cyclic C₁₋₁₀; alkyl group, and a C₁₋₄alkoxy group.
 2. The process of claim 1 wherein said inhibitor has a pKaof 4.8 to 14.15.
 3. The process of claim 1 wherein said inhibitor isselected from the group consisting of 2,4-pentanedione; 1-hexanoic acid;glycerol; and acetic anhydride; less than 1% (vol.)1,1,1,5,5,5-hexamethyltrisiloxane; less than 1% (vol.)1,1,1,3,5,5,5-heptamethyltrisiloxane; β-diketones RC(O)CH₂C(O)R;aliphatic carboxylic acids RCOOH; aliphatic dicarboxylic acidsHOOC—(CH₂)_(n)—COOH in which 1≦n≦8; phenols C₆R_((6-n))(OH)_(n) in which1≦n≦5; polyols CH₂X(CHX)_(n)CH₂X, in which X=H or OH but at least oneX=OH and 1≦n≦8; anhydrides RCH₂—C(O)—O—C(O)—CH₂R; hydrodosiloxanesR₃Si—(O—SiR₂)_(n)—OSiR₃, in which 0≦n≦8, all wherein R is individuallyselected from the group consisting of hydrogen, normal, branched orcyclic C₁₋₁₀ alkyl groups; and mixtures thereof.
 4. The process of claim1 including providing a free radical scavenger to saidcyclotetrasiloxane.
 5. The process of claim 4 wherein said free radicalscavenger is selected from the group consisting of:2,6-di-tert-butyl-4-methyl phenol, 2,2,6,6-tetramethyl-1-piperidinyloxy,2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, propylester 3,4,5-trihydroxy-benzoic acid,2-(1,1-dimethylethyl)-1,4-benzenediol, diphenylpicrylhydrazyl,4-tert-butylcatechol, N-methylaniline, p-methoxydiphenylamine,diphenylamine, N,N′-diphenyl-p-phenylenediamine, p-hydroxydiphenylamine,phenol, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate,tetrakis (methylene (3,5-di-tert-butyl)-4-hydroxy-hydrocinnamate)methane, phenothiazines, alkylamidonoisoureas, thiodiethylene bis(3,5,-di-tert-butyl-4-hydroxy-hydrocinnamate, 1,2,-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl) hydrazine, tris(2-methyl-4-hydroxy-5-tert-butylphenyl) butane, cyclic neopentanetetraylbis (octadecyl phosphite), 4,4′-thiobis (6-tert-butyl-m-cresol),2,2′-methylenebis (6-tert-butyl-p-cresol), oxalyl bis(benzylidenehydrazide) and mixtures thereof.
 6. The process of claim 5wherein said 2,6-di-tert-butyl-4-methyl phenol is provided in an amountof 50-500 ppm (vol.).
 7. The process of claim 5 wherein said2,2,6,6-tetramethyl-1-piperidinyloxy is provided in an amount of of50-230 ppm (vol.).
 8. A process for stabilizing1,3,5,7-tetramethylcyclotetrasiloxane against polymerization used in achemical vapor deposition process for silicon oxides in electronicmaterial fabrication comprising providing an effective amount of aneutral to weakly acidic polymerization inhibitor to said1,3,5,7-tetramethylcyclotetrasiloxane.
 9. The process of claim 8 whereinsaid inhibitor has a pKa ot 4.8 to 14.15.
 10. The process of claim 8wherein said inhibitor is selected from the group consisting of2,4-pentanedione, 1-hexanoic acid, glycerol, acetic anhydride, less than1% (vol.) 1,1,1,5,5,5-hexamethyltrisiloxane, less than 1% (vol.)1,1,1,3,5,5,5-heptamethyltrisiloxane and mixtures thereof.
 11. Theprocess of claim 8 including providing a free radical scavenger to said1,3,5,7-tetramethylcyclotetrasiloxane.
 12. The process of claim 11wherein said free radical scavenger is selected from the groupconsisting of 2,6-di-tert-butyl-4-methyl phenol,2,2,6,6-tetramethyl-1-piperidinyloxy and mixtures thereof.
 13. Theprocess of claim 12 wherein said scavenger is provided in an amount of50-500 ppm (vol.).
 14. The process of claim 12 wherein said2,2,6,6-tetramethyl-1-piperidinyloxy is provided in an amount of of50-230 ppm (vol.).
 15. A process for stabilizing1,3,5,7-tetramethylcyclotetrasiloxane against polymerization used in achemical vapor deposition process for silicon oxides in electronicmaterial fabrication comprising providing a neutral to weakly acidicpolymerization inhibitor to said 1,3,5,7-tetramethylcyclotetrasiloxaneand providing a free radical scavenger to said1,3,5,7-tetramethylcyclotetrasiloxane.
 16. The process of claim 15wherein said inhibitor is selected from the group consisting of2,4-pentanedione, 1-hexanoic acid, glycerol, acetic anhydride, less than1% (vol.) 1,1,1,5,5,5-hexamethyltrisiloxane and mixtures thereof. 17.The process of claim 15 wherein said free radical scavenger is selectedfrom the group consisting of 2,6-di-tert-butyl-4-methyl phenol,2,2,6,6-tetramethyl-1-piperidinyloxy and mixtures thereof.
 18. Acomposition of a cyclotetrasiloxane stabilizing against polymerizationused in a chemical vapor deposition process for silicon oxides inelectronic material fabrication, comprising; (a) said cyclotetrasiloxanehaving the following formula:

where R¹⁻⁷ are individually selected from the group consisting ofhydrogen, a normal, branched or cyclic C₁₋₁₀ alkyl group, and a C₁₋₄alkoxy group, and (b) a neutral to weakly acidic polymerizationinhibitor.
 19. A composition of 1,3,5,7-tetramethylcyclotetrasiloxanestabilized against polymerization used in a chemical vapor depositionprocess as a precursor for silicon oxides in electronic materialfabrication comprising 1,3,5,7-tetramethylcyclotetrasiloxane and aneutral to weakly acidic polymerization inhibitor.
 20. A composition of1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemical vapordeposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane and a neutral to weakly acidicpolymerization inhibitor and a free radical scavenger.
 21. A compositionof 1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemical vapordeposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising (a)1,3,5,7-tetramethylcyclotetrasiloxane, (b) a neutral to weakly acidicpolymerization inhibitor selected from the group consisting of2,4-pentanedione; 1-hexanoic acid; glycerol; acetic anhydride; less than1% (vol.) 1,1,1,5,5,5-hexamethyltrisiloxane; less than 1% (vol.)1,1,1,3,5,5,5-heptamethyltrisiloxane; β-diketones RC(O)CH₂C(O)R;aliphatic carboxylic acids RCOOH; aliphatic dicarboxylic acidsHOOC—(CH₂)_(n)—COOH in which 1≦n≦8; phenols C₆R_((6-n))(OH)_(n) in which1≦n≦5; polyols CH₂X(CHX)_(n)CH₂X, in which X=H or OH but at least oneX=OH and 1≦n≦8; anhydrides RCH₂—C(O)—O—C(O)—CH₂R; hydrodosiloxanesR₃Si—(O—SiR₂)_(n)—OSiR₃, in which 0≦n≦8, all wherein R is individuallyselected from the group consisting of hydrogen, normal, branched orcyclic C₁₋₁₀ alkyl groups; and mixtures thereof, and (c) a free radicalscavenger selected from the group consisting of2,6-di-tert-butyl-4-methyl phenol, 2,2,6,6-tetramethyl-1-piperidinyloxy,2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, propylester 3,4,5-trihydroxy-benzoic acid,2-(1,1-dimethylethyl)-1,4-benzenediol, diphenylpicrylhydrazyl,4-tert-butylcatechol, N-methylaniline, p-methoxydiphenylamine,diphenylamine, N,N′-diphenyl-p-phenylenediamine, p-hydroxydiphenylamine,phenol, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate,tetrakis (methylene (3,5-di-tert-butyl)-4-hydroxy-hydrocinnamate)methane, phenothiazines, alkylamidonoisoureas, thiodiethylene bis(3,5,-di-tert-butyl-4-hydroxy-hydrocinnamate, 1,2,-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl) hydrazine, tris(2-methyl-4-hydroxy-5-tert-butylphenyl) butane, cyclic neopentanetetraylbis (octadecyl phosphite), 4,4′-thiobis (6-tert-butyl-m-cresol),2,2′-methylenebis (6-tert-butyl-p-cresol), oxalyl bis(benzylidenehydrazide) and mixtures thereof.
 22. A composition of1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemical vapordeposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, and 2,4-pentanedione.
 23. Acomposition of 1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemicalvapor deposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, and 1-hexanoic acid.
 24. Acomposition of 1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemicalvapor deposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, and less than 1% (vol.)1,1,1,5,5,5-hexamethyltrisiloxane.
 25. A composition of1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemical vapordeposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, and glycerol.
 26. A compositionof 1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemical vapordeposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, and acetic anhydride.
 27. Acomposition of 1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemicalvapor deposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, 2,4-pentanedione and a freeradical scavenger selected from the group consisting of2,6-di-tert-butyl-4-methyl phenol, 2,2,6,6-tetramethyl-1-piperidinyloxyand mixtures thereof.
 28. A composition of1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemical vapordeposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, 1-hexanoic acid and a freeradical scavenger selected from the group consisting of2,6-di-tert-butyl-4-methyl phenol, 2,2,6,6-tetramethyl-1-piperidinyloxyand mixtures thereof.
 29. A composition of1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemical vapordeposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, glycerol and a free radicalscavenger selected from the group consisting of2,6-di-tert-butyl-4-methyl phenol, 2,2,6,6-tetramethyl-1-piperidinyloxyand mixtures thereof.
 30. A composition of1,3,5,7-tetramethylcyclotetrasiloxane, used in a chemical vapordeposition process as a precursor for silicon oxides in electronicmaterial fabrication, stabilized against polymerization, comprising1,3,5,7-tetramethylcyclotetrasiloxane, acetic anhydride and a freeradical scavenger selected from the group consisting of2,6-di-tert-butyl-4-methyl phenol, 2,2,6,6-tetramethyl-1-piperidinyloxyand mixtures thereof.